Decurling apparatus



Oct. 3, 1961 L. E. sEvlsoN 3,002,222

DECURLING APPARATUS Filed June 30, -1958 7 Sheets-Sheet 1 Oct. 3, 1961 L. E. sl-:vlsoN 3,002,222

DECURLING APPARATUS Filed June so, 195s 7 sheets-sheet 2 FIG. 5 A

INVENTOR ATToRN E Y Oct. 3, 1961 L. E. sEvlsoN DECURLING APPARATUS '7 Sheets-Sheet 3 Filed June 30, 1958 /N VAC/1) rae Oct. 3, 1961 Filed June 30, 1958 FIG. IO

L. E. SEVISON DECURLING APPARATUS 7 Sheets-Sheet 4 Oct. 3, 1961 L.. E. sEvlsoN 7 Sheets-Sheet 5 l w E L Y' #a l 1:', U l' T23 /65 fgf 52 .fatwa/ 5,/ 5; 7X/"Wir is .fa/mfr TTOZA/EV Oct. 3, 1 961 1 E. sEvlsoN DECURLING APPARATUS 7 sheets-sheet e FIG. I2

Filed June 30, 1958 FIG. II

ll//d HEATED ROLL FIG. 2

RN mm m5 5. M M

am im? oct. 3, 1961 L E SEVISON 3,002,222

DECURLING APPARATUS Filed June 30, 1958 7 Sheets-Sheet 7 MMA/'W ATTOR NEY 3,002,222 DECURLING APPARATUS Luther E. Sevison, Toledo, Ohio, assignor, by mesne assignments, to Ex-Cell-O Corporation, Detroit, Mich., a corporation of Michigan Filed June 30, 1958, Ser. No. 745,523

13 Claims. (Cl. 18-.,1)

This invention relates generally to a device forv straightening or decurling a strip of thermoplastic material. The present application is a continuation-in-part of my application Serial Number 265,734, now U.S. Patent No. 2,843,027, led January 10, 1952.

An object of the instant invention isito decurl thermoplastic material as it is Withdrawn in strip form from a .supply roll. One exemplary use of the invention resides in the making of thermoplastic boxes Where the individual sheets of thermoplastic material cut 4from 'a continuous `'strip should beperfectly flat and free from curls when 'delivered to the blanking station of the box making machine. By straightening the strip before successively severing same into sheets, the individual sheets can be prop,- erly and satisfactorily handled by such -a machine.

Other objects 4and advantages of this invention will hereinafter appear, and for purposes of illustration but not of limitation, an embodiment of the invention is shown on the accompanying drawings, in which- FIGURE l'is a vside elevation of the decurler mechanism for a plastic sheet; 4

.FIGUREZ is a diagrammatic view showingthe therm'oplastic sheet material being delivered from a supply roll to the heated roll which forms a part of the decurling mechanism; l f FIGURE 3 is a fragmentary side elevation, with some parts broken away for purpose of clarity, showing a portion of the decurler .and particularly the driving roll and heating elements, taken on the line 3-3 of FIGURE 1;

FIGURE 4 is a fragmentary side elevation on the line 4-4 of FIGURE 1;

FIGURE 5 is a transverse sectional view on the line 5-5 of FIGURE 1, showing the iio'ating roll and associated parts;

FIGURE 6 is an enlarged vertical sectional View of the line 6 6 of FIGURE 4;

FIGURE 7 is a wiring diagram for the heating ele- 'ments by which the plastic sheet is heated during the decurling operation;

FIGURE 8 is a fragmentary view, largely in section,

showing the incher feed and feeding mechanism for advancing the sheet to the blanking mechanism (not illus- .trated);

FIGURE 9 is a side evelational view corresponding generally to FIGURE 1 but showing a diiferent embodiment involving both a heating and cooling of the thermoplastic strip;

FIGURE 9A corresponds to FIGURE 9 but depicts the apparatus in a non-heating position;

FIGURE l0 is a sectional view taken in the direction of line 10-10 of FIGURE 9;

FIGURE 11 is an outwardly facing front elevational View of one of the heating units depicted in FIGURE 9;

FIGURE 12 is a side elevational view of FIGURE l1;

FIGURE 13 is a sectional view taken in the direction of line 13-13 of FIGURE 9 showing some of theconstructional details of the cooling drum;

FIGURE 14 is a sectional view taken in the direction of line 14-14 of FIGURE 13, the view showing further details of the cooling drum, and

FIGURE 15 is 4a fragmentary side elevational view closely resembling FIGURE 9, but showing a slightly modified actuating mechanism for the heating units.

Referring to FIGURES 1 and 2, it will be understood 2,002,222 Patented Oct. 3,v 196,1-

2 that in the exemplary situation the supply roll of plastic sheet material from which the box is formed, has its free end passed over a heated roll H, which is a part of the decurling apparatus which will be more fully explained hereafter. From this continuous strip S of sheet material, a section is severed, that section being of a predetermined size suflicient for blanking operations. The apparatus for decurling the continuous strip of sheets from a supply roll R comprises a standard, having a base 16 from which rises a pair of laterally spaced posts 17 arranged rearwardly of the base 16. Adjacent to the front end of the base 16 rises a pair of laterally spaced columns 18 of tubular form, which extend vertically a substantial distance beyond the posts 17. Connected to and supported by posts 17 and columns 18 are horizontal supports 19 on which the roll R is suitably mounted for turning movement. As shown, spaced rearwardly of the supply roll R is a reserve roll R which can be placed in use when the supply roll R is exhausted.

From the supply roll R the strip S extends upwardly and about the heated roll H, thence downwardly and inwardly over a guide roll 20, which is carried by brackets 21 secured to the upper portions of the columns 18. From the guide roll the strip extends downwardly to a oating roll 22. Arranged between the guide roll'2'0 and the iloating roll 22 is a pair of laterally spaced curved guide fingers suitably carried by the columns 18. These fingers engage opposite edge portions of the strip S as the latter advances and are so shaped to trough or cause the edge portions of the strip to be givenA a re'- verse curl, lengthwise of the sheet, for the purpose of assisting in straightening out the continuous sheet and to obtain a strip, which is as at and free from undulations and curls as is possible.

From the floating roll 22 the strip S passes o'ver a. guide roll 23 to the feeding mechanism of a box making (not shown) machine. Sufiice it to say at this time that the feeding mechanism operates in a step-by-step manner whereby the strip S is pulled for a predetermined distance after which the feed remains quiescent until the next successive pull or advancing movement imparted to the sheet.

Spaced above the roll H is a canopy 24 which is arcuate in cross section and carries on its under surface an electrical heater for supplying radiant heat to the strip S as it passes over the roll H. As shown in FIGURE 7, the heater 25 has three sets of heating units 2SA, 25B and 2SC, these being of varying resistances in order to gencrate varying degrees of heat in accordance with the demands of service. 'Ihe particular electrical arrangement form-s no part of this invention. Suflce it to say that a main switch 26 is electrically connected to a relay 2.7 suitably connected through the switches leading-to the individual groups of heating coils. Current is supplied from the lines 28 yand 29, and by actuating the main switch 26 and one or another of the switches for the respective units 25A, 25B and 2SC, the proper or desired'radian heat for the roll H may be readily obtained.

The exterior of the roll H is covered by cloth to provide a relatively soft surface over which the strip S may'pass freely without scratching it. The roll H is of substantial size and disposed within the roll and suitably connected for driving it is an air engine 31 of the piston and cylinder type. Since air engines of this type are well known in the art and since the particular construction forms no part of this invention, detailed description thereof is not considered necessary. Air under pressure is supplied to the air engine 31 by a tube 32 which extends downwardly to the lower end of a valve housing 33 suitably clamped to one of the columns 18 about midway of its height. Air under pressure is supplied to the upper end of the valve housing 33 through a tube 34 from a suitable so'urce,.a manual valve 35 being disposed adjacent the upperv end of .engine 3ft. "parts a step-by-step movement to the strip S and is not in 3 the valve housing 33 for controlling the introduction of compressed air to the housing.

Referring particularly to FIGURE 6, a passage 36 extends vertically through the housing 33 and arranged Within this passage is a poppet type valve 37, which is vertically reciprocable toward and away from a valve seat 3.8. Connected to the underside of the valve 37 and depending therefromr is a tapered rod 39 constituting a metering valve. The metering valve 39 passes through a sleeve 4t?, and the further upwardly the metering valve 39 moves relative to the sleeve. et), the greater will be the amount ofA air which is allowed to pass between the valve and the sleeve d0. A passage 41 connects the portionA of the passage above the sleeve 40 with that portion of the passage below the sleeve and a manually operated needle. valve 42,. controls the passage of` air through the passage or bypass 41. Connectedto the lower end o the metering valve 39 and depending therefrom Vis a guide rod 43 which passes loosely through a tubular guide 4e. Connected to the upper end ofthe valve 357 is a raclr 45 and at the upper end ofV the. rackdS extends a vertically disposed rod te which passes loosely through a guide il.v Meshing with the teeth ofthe rack Sis arpinion 47 which is oscillatably mounted in va cavity formed in the valve housing 33.

Fixed tothe pinionishaft on the outside of the, housing 33 is/an operating arm 48 and, pivoted to the free end of thezarmd is a depending link 49. The lower end of the y49 is pivoted to an arm Sil which is mounted upon andxed to a transverse shaft 5.1. 'lhe transverse shaft 51 has its end portions rotatably mounted in transverse 'bracket arms 5 2, the inner ends of which are. clamped to the upright columns It. Fixed to the-end, portion of the :shaft 5l is .aknurled operating wheel 53 to enable the wheel and shaft Sl and associated parts to be moved by hand, `when sodesired.

Fixed to an intermediate portionof the shaft .Si 1s an arm Sie which projects forwardly towards the columns 18 Vand rigid with its opposite end is a yoke 5S carrying the oating roll 22. In Yorder to counterbalance the weight of the roll 22 and associated parts, a torsional spring S6 has one end xed to one of the braclcet arms 52, 1s

awound about the shaft 51 and has the opposite end fixed tothe shaft, as indicated on FEGURE 5.

Fixed to the shaft 5,1 adjacent to the arm 5i? 1s a relatively short arm 57 which cooperates. with a ,switch 5S.. 'When the roll 2.2 fails downwardly upon release .frornthe more pliable and is in the desired condition for decurling.

'It `will be noticed that the strip as it leaves the heater roll H is directly given a reverse bend as it passes over the guide roll 20 restoring the strip to a substantially at condition. Since there is a tendency of the side edge portions of the strip to curl, the strip then passe-s lbetween the yguide ngers 59 supported on a transverse rod 60 which create a trough-like etiect and is found to eliminate curling difficulties lengthwise of the sheet.

Advancing movement is imparted to the strip S .causing vit to unwind from the roll R by the operation of the air `inasmuch as the subsequent mechanism imthe nature of a continuous uniform feed, it is necessary "that lthe air engine 3l operate Vat dilerent rates of speed.

It will be apparent that .the operation of the air engine 31 is controlled by the movement of the iloating roll 22 and when a pull is exerted on the strip S by the mechanism in advance of the guide roll 23, the floating roll 22 is caused 4to vswing upwardly, such, for example, as to `the broken line position shown in FIGURE l. When this action takes place, throughthe connections described, -it will be understood that the metering valve 39 (FIGURE 6) is moved vertically upward allowing a greater volume of air under pressure to pass to. the air engine. On the other hand, when, theiloating roll 2Q moves downwardly, through the actionofrthenreterine valve 3.9;, the volume of: air te the air motor 31, is gradually:- reduced... thereby slowing up the air engine. ln the event that;4 the strip should brealc or'forhotherreasons the floating roll 22 drops to its lowerrnost position, theA valve 357 is then moved to its seat 38, cutting oi 4the flow of compressed air to the air engine. At the same time, the limit switch 5S wijllbe actuatedto shut off the operation of the heater. A predetermined aiuo-unt of compressed air canv be bypassed through the bypass il onmanipulation of the valveZ for supplementing the volume of air permitted to Flow by the metering valve 39.

For imparting recurrent advancing movement to the strip S for a relativelyshort distance; a feeder or ingher 70 is provided and consists of pairs of vertically aligned friction rolls for grip 'ng the strip S therebetween; as shown in'FlG-URE 8. The incherinciudes a transverse shaft '71 on which are fixed for rotanti a pair of rubber covered, rolls 72. A similar shaft-rollerariangernent is disposed beneath the table, thelatter roller being identitled the reference numeral 75 on FIGURE 8.

It willbe understood that the ineher 7i? advances the strip of plastic sheet material a short distance s uiiicient to enable certain gripping elements to engage it and advance it further to the blellking .st-egt?, Which vforms n o part of the instant invention and therefore isl not hereindepeted. After the strip has been advanced asufripieutdistance suitable for a blank, that portion is severed from the continuous strip by a euto mechanism *77.

Reierring particularly to FIGURE 8, it will be understood that after the ineher '79 has advanced the continuous strip S of sheet material a short distance beyond the cutoff' 77, a reciprocator-y feeding device grips the adretled Y.edge of A the sheet and pulls it forwardly for a distance suitable for a box blank; thereupon the eutoi operates to sever that section Vfrom the continuous strip S. A carriage 82 is adapted to reciprocate horizontally toward and away from the eutohf 77. Op the upper portion of the carriage 82 is a notched head 234 adapted Vto receive the forward free end of the strip therein. As indicated on FIGURE S, the notchedv head 84 has, an intermediate recess in which a pivoted lahrnping or gripping plate or finger 35 operates. YThe clamping or gripping plate r$55 is pivotally'mounted at 6 its rearward end and has a depending actuating armV 3 7, fthe lower end of which is in the form of a yoke to straddlc a spool 8S. The spool $3 forms a part of an elongated piston rod -89 which, as shown on FIGURE 8, has a piston 90 at one end mounted for reciprocation with@ a cylinder u91. At the opposite kend or the pistou lrod 89 is a piston 92'Which operates to release the gripping or clamping plate kv85.

Considering Vnow the embodiment pictured Vin lF lfiljlluE 9, it may be explained that like parts have been assigned the same reference numerals used lin describing the previous embodiment. At the outset, though, it will ybe perceived that the strip instead of inclinirig upwardly as Vin 'FIGURE l, is constrained to follow a vertical path after leaving the Aroll R by reason of a guide roll 96 carried by brackets 97 extending from the columns 13.

Disposed above the guide Aroll Sio is Va pair o confronting heating units 98 and ,199. Generally speaking, the units 9,8, 99 are duplicates of each other. However, the unit 98 is -slighby shorter and is equipped with a'heat baille in the form of an angle member ltl. The somewhat` larger unit 99 carries at its upper end an upstanding flange itil for guiding the strip S as it `leaves the heating units. 'The construction of the heating unit -99 is best viewed in FIGURES ll and l2. As shown .in

this particular igure, the unit 99, as does the unit 98, comprises a rectangular pan 104 having a bottom 105 v and sides 106. A panel 107 is fxedly spaced somewhat Athrough the agency of a manually actuatable switch 114 that normally remains closed.

The heating units 98, 99 are mounted so as to be retracted or separated from the strip S. Accordingly,

a lower bracket i115 is iixedly supported by one of the ,columns 18 at one elevation, and a similar bracket 116 is attached to said column an an upper elevation. The lower bracket 115 supports a pair of horizontal parallel shafts 117 and 118, whereas the upper bracket 1.16 supports a pair of shafts 119 and 120.

The mechanism for rocking the shafts I117, `118, 119 and 120 and thereby operating the heating units 98, 99 will now be described. in achieving their aim, an air cylinder 123 has its closed end pivotally supported to a bracket 124 on one of the columns 18. Contained within the air cylinder 123 is a projecting piston rod 125 that is pivotally connected to an actuating arm y1.26 keyed to the shaft 119. While this accounts for the rotation or rocking of the shaft 119, it is necessary to rotate the lower shaft 117 in unisonvwith said shaft 1-19. To do this a take-off arm 127 has articulatively attached thereto a connecting link 128 extending downwardly to an actuating arm 129 on the shaft 117. To rotate or rock the upper shaft 120, a horizontal link 131 extends between one end of an arm '130 on the shaft 119 and an arm 132 on the shaft 120. Similarly, a horizontal link 133 extends between one end of an arm 134 on the lower shaft 117 and .an arm 135 on the shaft 118.

The physical withdrawal of the heating units 98, 99

vis achieved by way of arms 136, 137, 138 and 139, each numeral denoting a pair of such arms. The arms '136, mounted on the shaft 119, are pivotally connected to laterally spaced ears 140 carried by the heating unit 98, whereas the arms 137, mounted on the shaft F117, are pivotally connected to laterally spaced ears 141 also mounted on this heating unit. The arms `138 are in similar fashion pivotally connected to a pair or" ears 14011 on the heating unit 99 and the arms 139 are connected to a pair of ears 141a also located on this unit.

' In this way, upward movement of the piston rod 125 effects simultaneous separation of both of the heating units 98, 99. Later on the manner in which compressed air is supplied to the cylinder 123 will be presented.

Rotatably supported at the topsof the columns 18 is a cooling drum or roll C, depicted in detail in FIGURES 13 and 14. As can be discerned from FIGURE 13, the cooling roll C comprises. an outer cylindrical tube 143 having an imperforate end plate 144- at one end and a perforated end plate y'145 at its other end, the latter having a series of angularly spaced perforations or apertures 146 through which cooling air furnished to this roll C can exit. v

Concentrically disposed within the outer tube 143 is a somewhat shorter inner tube 147. The concentricity is maintained by means of a plurality of U-shaped spoke ns`148 (see FIGURE 14) having their bight portions welded to the outer tube 143 and their leg portions Iwelded to the inner tube 147. These spoke fins 148 provide a number of parallel passages v149, 159. Since the inner tube 147 and the fins 148 are shorter than the outer tube 143, an end chamber A151 is formed, this chamber G providing'cornmunication between the bore of the inner tube 147 and the various passages 149, 150.

A cooling roll shaft 152 extends axially through the inner tube 147, being anchored at one end to the end plate 144 and at its other end to a shaft bracket 153. The shaft is not intended to rotate, the cooling roll instead being designed to rotate about the shaft by reason of a ball bearing assembly 154 contained in the end plate 144 and a needle bearing assembly 155 contained in the end plate 145. A frame member 156 is mounted at the upper end of one of the columns 18 and a frame member 157 is mounted atop the other column 18. The frame member 156 journals a stub staft 158 splined at its free end for coupling to an air engine such as the air engine 31 that has been perviously alluded to. Since the stub shaft 158 is mechanically connected to the end plate 1144, it can vbe appreciated that the cooling roll C will be rotated when the engine 31 is operated. The frame member 157 xedly supports the bracket 153, the end plate 146 being free to rotate with respect thereto by reason of the bearing assembly 155. It will be observed that the frame member 157 contains a plurality of apertures 159 permitting free escape of the air exiting through the discharge apertures 146.

The cooling air is introduced into the cooling roll C viatthe shaft bracket 153, this bracket being of hollow construction and provided with a plurality of entrance apertures 160. A blower `161, powered by a suitable motor 162, furnishes the cooling air to the bracket 153 for passage through the cooling roll C.

From the description that has been given up to this point it is believed apparent that the cooling roll C is intended to not only cool the strip S after heating thereof by the heater units 98, 99 but that it is also intended much the samevcapacity as the heating roll H of the earlier-described embodiment. Accordingly, air under pressure is supplied to the air engine 31 through the Valve housing 33 and the tube 32, the valve 33 being controlled by the oating roll 22, as has already been described in conjunction with said earlier-described embodiment.

What has not as yet been explained is how Vair is furnished to the cylinder 123 to efect a `bringing together of the separable heating units 98, 99 from the position shown in FIGURE 9A to their normal operating position pictured in FIGURE 9. In the present arrangement, the relatively short arm 57 is utilized to actuate a switch 165 in circuit with a solenoid 166. The solenoid 166, when energized permits air under pressure to flow through an air valve 167 to the upper end of the air cylinder 123 Via a tube i168. Air so supplied `to the air cylinder 123 will cause its piston rod 125 to be urged downwardly, thereby rocking the shaft 119, and indirectly the other shafts 117, 118 and 120', in a direction to move the heating units 98, 99 toward each other into the position illustrated in FIGURE 9. Such action occurs when the floating roll 22 is in itsupper position, as shown n FIGURE 9, the switch i165 being oriented with respect to the arm 57 so that it is closed when the arm y is rotated in a counter-clockwise direction as viewed in FIGURE 9. In other words, provision is made for urging the heater units 98, 99 together when the system is functioning properly. Should the strip S break or for some other reason drop to its lower solid line position, as presented in FIGURE 9A, the switch 165 is opened, and the solenoid 166 thereby deenergized, to close the valve 167 with the consequence that air to the cylinder 123 s cut off and that air in the tube 168 is exhausted through the exhaust port of said valve 167.

In the specific arrangement set forth in FIGURES 9 and 9A, it is planned that the heater units 98, 99 be spring actuated toV their separated position when no air lis equipped with a coil spring-idilinterposed between the -upper end of the airlz'fadfanplate Jor Washer i7@ carried by the proje 'irgend thedpiston tad 125 It can btt readily Stati?, itlt @slitta-t1? tliatwhep rio compressed air is furnished to the -cylinderull the spring i659, which is compressednwhen 'the heaterkunits r91S, 52 are together, expands, there y urging or pushing the piston rod 12S upwardly asvievvedn in'VFTGVURE Through the agency ofthe spring 'roti-th lflef'iter esta aromatase fti- 't i1 l each other, should there be either an elec `l or pneumatic failure. This is the positionshovvri'inflfi GUEB Stated some vhat more specifically, should'el ctricn power to the solenoid 165 be lost, airwill b'e'bled from the cyiinder 123 via the now shutoii"V air valve loand the `spring 69' Will push the piston rod 12S; u Y n ila u. the heater units 98, '92. the same" token, Vthe auppiy of compressed air 'twofthefairi '1557 Yhe lost, the spring iti? will imi mediatelyy expand to W the same end result, that beiugto er'ctisfepa heater units BSQ` their? reiatio^-nshipv with the thermoplastic strip` In otherwords the heater units 581, 99 move from the pos ion in FGURE Qft'o the position in FGR'QA, y" n WN Y' l While it is felt that the preceding spring arrangement wili be the preferred one ina riumherof'iiis sfnonetheiess the "invention also envisions "a 'oompletely'peumatic operation of the cylinder 125i.A *Attention* is,

therefore, directedwto then fragmentary views'tiforth in FIGURE 15. I

l Inth'isi situation, two tubes todo, i681; lead from "airmvalvemida to opposite ends of a cylinder Vigie. During normal operation the energization of `the 'solenoid loovvili furnish air under pressure to the upperf ,endof 4thefcylinder i235: via tube 168e and the pistonrod 125' vvilhhe forced downwardly just as inthiefprevious spring 'emhodiment. When the solenoid 166 ismd uergizefd, though, compressed air is `iiql'stead via the` tube 1635 thereby to forca the Pisten tati 11.25" upwardly' with a concomitant separation or retraction n.of the heater units 98, 99. Thus, in this somewhatmodiied version the air cylinder 123e is double acting depending Uupon Awhether air is fed to the lower or upper end thereof."

1.a Summary, the tmbtedimat at FLGURE '1" adds heat to the thermoplastic strip by Way of the/heater QS and roll H, the heat being cut .gli during anyk stoppage at the Stript travel In Saat@ Situations 'ssntlcilly where the strip S is of relatively thin gauge, the'residual heat vis objectionable Alto, there is Setlist/hat O f t? .lag when the System is restarted., Siate, tias hasta! l it abt instantaneous itl @Online tttittlp t9. .the ditsftihl'tm- -perature When such ditlicuities are experienced, consideratin will be given tothe tatd iiiitftittert Of molines 9 and i5.

in a@ embodiments set .fait a Piensas? @at 15, theheating units 93, 959 remain ener during work. sinistres, but are moved apart S9 es aat ttf .eadaastt 4the strip S. ByV so doing, the heat immediately reapplied to the strip when feeding of said strip is resumed. Aliso, the residual heat problem is obviated. hurther, the cooling action furnished hy roll C assists in the decurling achievement because `the strip S'is Tonite IVtaut when passing thereover.

NIt is to be understood that `numerous changes may be eii'ected in details of construction, arrangement, operation and Choice 0f materials, Withttttt seattt'as tram the Spirit of tttt invention, @spatially at' that@ iti the ,appended claims. y

` What is claimed is:

1.4A decurling device for a continuons iengtli of plastic sheet material comprising a heater, avr'oil for advancing the sheet past the heater, Ymeans for driving the roll, feed means operable intermittently yto 'pull lthe sheet forwardly, a soating rail aboutwhich Isheet The same ys olerroid is used, 'a vrifiptliiied air valve 167e is employed.

passes and adapted to risel and fall according to the action of the feed""meansfnd'eaiis responsive to the rising' and falling movement of'said floating roll for controlling said driving means.` l

" 2. A 'decurling device' as claimed in claim 1 in which said driving meansincludes a pneumatic Vengine and said responsive means includes valve 'means controlling the ainsupplytoV said engine in accor'danoeA withthe rising and yfalling movement of said Hoating roll 'thereby to accelerateur Ad'ecelerate the enginev speed.

i 3, Ad'ecurlingk device as claimedin'claim 2, comprising a pivotallyimounted lever forms'aid floating roll, and said valve means 'comprising a 'longitudinally shiftable metering` device forincrea's'ing or. decreasintg'fthe' volume of air supplied tothe Yengineaccord-ing tothe position of said lever. 4. A decurling device as claimed in claim 3, comprising a bypass associated with"iaidieteiihg device, and amanualvalve for Yioii'trolliiig`the 'air flow" through the byfp7ass"`thereby to atr'd' nualcoritrol'or V`the engine peed...

S'A decurling device as claimed in claim 4, in which the heater Ac'oirfprises an reletical'device; and switch for rendering the electrical' device inoperative upon breaking the continuity `o'fith'e sheet'. 't

'l 6`A decurling device "a's claimed in claim 4 in which rsaid heater isfiretractable"felative'ito "sfa'iid'sheet material,

and meansV for'r'etracting I 'dheateruponbreaRng:the continuity ofthe sheet'f m' M 7.` A' decurling device for a continuous length of plastic shetmaterial comprising a pair io'f-lr'etractfably mounted heateruni't's, me VYs'to dvanc'ithe sheet between said heater'nit's, "automatlc m ns "forgulating'th operation of said advancing means iin'iesponseto theocrnands o service, an aiFcylindei-"foi: urgin'gmsaid heater' units toward saidsheet, aridauto'triatic meansitore'dering said advancingnrneans inetiectivle'in vthefeveiit of breakingy the 'continuity ofthe: sheet,n said lasik-m.'en'tiorled means also o'asnfg' said aiii'cyliiider t'r'trctsaid'heatr units.

8L A decurling device as claimed in claim 7- in which the advancing means includes'a cooling 4foll about which said sheetpassesmafte'r hefa therofby V`s""`d" heater umts. 49. A decurling device as claimed in claim 8` in which the advancing means further includes a pneumatic engine for driving the cooling roll, valve means for'contr'olling the air supply to said engine, `feed means operable intermittently to pull the vsheet'forwardly,a Heating roll about which the sheet passesL andadapted to rise and fall according to theact'ioii of the feed means, and van operative connection between said floating roll and valve means for actuating the latter in response to the positionof the ioa't'ing roll thereby to'accelerate'or decelerate the engine speed. A

10; A decurling device for a continuous length of plasticsheet material Vc'c'mprising a pair of retractably mounted, vertically disposed heater units, `a cooling roll above said heater units about which the heated material passes to be vthereafter directed downwardly, a floating roll under which said material passes after cooling thereof, means controlled-by said oating roll for actuating said heater units between a position in proximal relationship to the adjacent sheet material and a position in a more substantially spaced relationship to the adjacent sheet material than the rst mentioned positionand additionai means controlled by vsaid .floatingmroll 4for determining .the rotative speed of said cooling roll.

ll. A decurling device 'as' claimed in Aclaim` l() including feed meus"operable intermittently to'pull the'fsvheet vl)forwardlyafter passing yabout said floating roll.Av

l2. A decurling devicefor a'continuous'iength of plastic sheet comprising means for holding va Asource of supply of sheet material, ah'eater unit, means" for-advancing said sheet material past theheatr unit, means for sensing the tension in said sheet material lafter it References Cited inthe file of this patent has passed lthe advancing means, vand means responsive UNITED STATES PATENTS to saidtenslon means for controlling the speed of said advancing manS 2,320,115 Young May 25, 1943 10 OTHER REFERENCES Heating With Far 1nf1'aRed/(Perrotta), published in Modern Plastics, August 1953, pages 109-1/15. 

